共查询到20条相似文献,搜索用时 0 毫秒
1.
介绍一种新的量子隧穿———非线性朗道-基纳隧穿.这种隧穿一般发生在有相互作用的二能级系统中,比如光晶格中的玻色-爱因斯坦凝聚物和分子磁体.相对于传统的线性朗道-基纳隧穿,非线性朗道-基纳隧穿由排斥相互作用带来的非线性会增强隧穿的概率.特别是当非线性非常强时,系统的绝热性会遭到破坏;一个无穷小的线性驱动都会造成有限的隧穿概率. 相似文献
2.
We address the response of a two-mode Bose-Einstein condensate to a biharmonic high-frequency driving field that directly couples the two mode. By use of a high-frequency approximation we find that asymmetric biharmonic high-frequency driving yields new effects on Nonlinear Landau-Zener tunneling as compared to a symmetric off-diagonal modulation. In particular, we detect an unclosed loop structure and the disappearance of the energy level below the loop structure. 相似文献
3.
4.
5.
6.
We study the hamiltonian and dissipative dynamics of a system undergoing a sequence of level crossings. The resulting Landau-Zener effect makes a new implementation of a general single qubit gate possible. In the dissipative case, with a periodic bias, the level crossing counteracts the interlevel relaxation and drives the system toward a two dimensional attractor. This feature can in principle be used to implement quantum memory devices of new type. 相似文献
7.
We study tunneling of a Bose-Einstein condensates confined in a effective double-well potential (a single well with a spatially magnetic modulated scattering length, actually), called pseudo double-well trap, in which the interaction of atoms characterized by the s-wave scattering length a s can be widely tuned with a magnetic-field Feshbach resonance. As a result, corresponding to different nonlinear parameters, the energy levels of the nonlinear Schrödinger equation can have complex structures in their dependence on the bias between the wells. We discuss the emergence of looped levels, which lead to a breakdown of adiabaticity that the Landau-Zener transition probability does not vanish even in the adiabatic limit. Moreover, we also find that the Landau-Zener tunneling in the pseudo trap show many striking properties distinguished from that of the real trap model (where the barrier is created by the external potential). Possible experimental observation in an opticallyinduced photonic lattices in a photorefractive material is suggested. 相似文献
8.
在加速光晶格中玻色-爱因斯坦凝聚体(BEC),当同时考虑两体和三体相互作用时,其能级结构、隧穿率出现了独特的特性.在一维加速光晶格中的BEC,当两体和三体相互作用参数满足一定条件时,非线性两能级体系的能级结构中出现了圈结构,研究得出了圈的宽度随两体和三体相互作用参数变化的关系,并由此分析圈结构的出现及其大小对BEC隧穿率的影响. 相似文献
9.
魏秀芳 《原子与分子物理学报》2015,32(6)
在加速光晶格中玻色-爱因斯坦凝聚体(BEC),当同时考虑两体和三体相互作用时,其能级结构、隧穿率出现了独特的特性.在一维加速光晶格中的BEC,当两体和三体相互作用参数满足一定条件时,非线性两能级体系的能级结构中出现了圈结构,研究得出了圈的宽度随两体和三体相互作用参数变化的关系,并由此分析圈结构的出现及其大小对BEC隧穿率的影响. 相似文献
10.
We propose a new type of interferometry, based on geometric phases accumulated by a periodically driven two-level system undergoing multiple Landau-Zener transitions. As a specific example, we study its implementation in a superconducting charge pump. We find that interference patterns appear as a function of the pumping frequency and the phase bias, and clearly manifest themselves in the pumped charge. We also show that the effects described should persist in the presence of realistic decoherence. 相似文献
11.
An explicit nonlinear superposition formula for the nonlinear Schrödinger equation is derived for the first time. 相似文献
12.
One may probe coherence of a qubit by periodically sweeping its control parameter. The qubit is then excited by the Landau-Zener (LZ) mechanism. The interference between multiple LZ transitions leads to an oscillatory dependence of the energy absorption rate on the sweeping amplitude and on the period. This interference pattern allows to determine the decoherence time of the qubit. We introduce a simple phenomenological model describing this interferometer, and find the form of the interference pattern.Received: 21 October 2003, Published online: 8 December 2003PACS:
03.67.-a Quantum information - 85.25.Dq Superconducting quantum interference devicesD.A. Ivanov: Present address: Paul Scherrer Institute, 5232 Villigen PSI, Switzerland 相似文献
13.
14.
15.
16.
J. E. Avron M. Fraas G. M. Graf P. Grech 《Communications in Mathematical Physics》2011,305(3):633-639
We consider a family of time-dependent dephasing Lindblad generators which model the monitoring of the instantaneous Hamiltonian
of a system by a Markovian bath. In this family the time dependence of the dephasing operators is (essentially) governed by
the instantaneous Hamiltonian. The evolution in the adiabatic limit admits a geometric interpretation and can be solved by
quadrature. As an application we derive an analog of the Landau-Zener tunneling formula for this family. 相似文献
17.
18.
19.
We report on an experimental study of quantum transport of atoms in variable periodic optical potentials. The band structure of both ratchet-type asymmetric and symmetric lattice potentials is explored. The variable atom potential is realized by superimposing a conventional standing wave potential of lambda/2 spatial periodicity with a fourth-order multiphoton potential of lambda/4 periodicity. We find that the Landau-Zener tunneling rate between the first and the second excited Bloch band depends critically on the relative phase between the two spatial lattice harmonics. 相似文献
20.
Jona-Lasinio M Morsch O Cristiani M Malossi N Müller JH Courtade E Anderlini M Arimondo E 《Physical review letters》2003,91(23):230406
Using a simple model for nonlinear Landau-Zener tunneling between two energy bands of a Bose-Einstein condensate in a periodic potential, we find that the tunneling rates for the two directions of tunneling are not the same. Tunneling from the ground state to the excited state is enhanced by the nonlinearity, whereas in the opposite direction it is suppressed. These findings are confirmed by numerical simulations of the condensate dynamics. Measuring the tunneling rates for a condensate of rubidium atoms in an optical lattice, we have found experimental evidence for this asymmetry. 相似文献